Mitsubishi Electric Melsec QJ71LP21 Reference Manual page 258

7 APPLICATION FUNCTIONS
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(Example 2) When executing instructions from a redundant system
If system is switched in a redundant system during execution of an
instruction, the instruction will be discontinued in the redundant CPU of
the new control system and will not be completed.
Using the SM1518 (one scan ON after system switching) and the
complete signal, create a program that any instruction being executed will
be continued by the new control system even when the system is
switched in the redundant system.
Processing program at normal completion
Processing program at abnormal completion
MELSEC-Q
Arrival confirmed/clock data setting
Channel used by host station
Target station CPU type
Target station network number
Target station number
Number of resend times
Arrival monitoring time
Written data length
Written data
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